This invention relates to a synchronizer having means to limit synchronizing force.
Synchronizers for use in multi-ratio transmissions are well known. Such synchronizers include pairs of friction and jaw members for respectively synchronizing and positive clutching a gear to a shaft, pre-energizer assemblies for engaging the friction members in response to initial engaging movement of a shift sleeve, a hub rotatably fixed to the shaft and having external spline teeth slidably receiving internal spline teeth of the shift sleeve which often defines one of the jaw member pairs, blockers for arresting engaging movement of the shift sleeve until synchronization is reached and for transferring a shift force from the sleeve to increase the engaging force of the friction members.
An object of this invention is to provide a synchronizer with means to prevent excessive pressure on friction surfaces therein.
According to a feature of the invention, a synchronizer for frictionally synchronizing and positive connecting first and second drives is disposed for relative rotation about a common axis. The synchronizer comprising first jaw means axially movable from a neutral position into an engaged position with second jaw means for positive connecting the drives in response to engaging movement of the first jaw means by an axially directed first shift force. A first friction member is axially movable into frictional engagement with a second friction member in response to the engaging movement of the first jaw means for producing a first synchronizing torque. First and second blocker means prevent asynchronous engagement of the jaw means and transmit the shift force to the first and second friction members.
The improvement is characterized by first limit means producing a first counter force for decreasing the amount of the first shift force transmitted to the first and second friction members in response to the synchronizing torque exceeding a first predetermined amount.